03/27/2026
By Danielle Fretwell

The Francis College of Engineering, Department of Civil and Environmental Engineering, invites you to attend a Doctoral Dissertation defense by Gustavo Salcedo on: "Occurrence, Distribution, and Ecological Impacts of Drugs of Abuse in Aquatic Environments."

Candidate Name: Gustavo Salcedo
Degree: Doctoral
Defense Date: Friday, April 10, 2026
Time: 10 a.m. -noon
Location: ETIC 445. This defense will be held via synchronous in-person and virtual meeting.

Committee:

  • Advisor: Sheree Pagsuyoin, Civil and Environmental Engineering, University of Massachusetts Lowell
  • Frederic Chain, Biological Sciences, University of Massachusetts Lowell
  • Arghavan Louhghalam, Civil and Environmental Engineering, University of Massachusetts Lowell
  • Alexander van Nuijs, Department of Pharmaceutical Sciences, University of Antwerp
  • Marta Gomez-Chiarri, Fisheries, Animal, and Veterinary Sciences University of Rhode Island

Abstract: 

Drugs of abuse (DAs) are substances with a high potential for addiction, encompassing both prescribed medications and illicit drugs. Their high global consumption, incomplete removal during wastewater treatment, and continuous discharge into surface waters have led to their widespread presence in the environment. Many DAs are highly psychoactive and biologically active, with several exhibiting environmental persistence. While the aquatic ecotoxicity of other micropollutants, such as estrogens and antibiotics, has been extensively studied, the effects of DAs on aquatic organisms remain poorly understood. There is a critical need to assess the ecological risks associated with their presence in aquatic ecosystems. The overall goal of this research was to evaluate the environmental distribution and impacts of DAs in aquatic systems. Specifically, this study aimed to: (i) assess the distribution of DAs in surface waters, (ii) evaluate their effects on aquatic indicator organisms, and (iii) characterize the ecological risks associated with residual DA discharges. 

Environmental occurrence was investigated regionally in Massachusetts and the headwaters of New Hampshire through field sampling and globally through a literature review. Field sampling was conducted in four major urban rivers in (Merrimack, Blackstone, Connecticut, and Charles Rivers), along with coastal sampling in Massachusetts Bay. Samples were analyzed for 10 target DAs (benzoylecgonine, cannabinol, cocaine, codeine, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine, fentanyl, methadone, ketamine, methamphetamine, and tramadol) selected based on high global consumption and frequent detection in wastewater and surface waters. 

Literature data mining was performed to assess reported concentrations in riverine systems worldwide. In New England, DA concentrations reached up to 10^2 ng/L, while globally, compounds such as cocaine, fentanyl, and methadone have been reported at higher levels, up to 10^3 ng/L. Ecotoxicity was evaluated using oyster larvae (Crassostrea virginica) and Daphnia magna, with endpoints including survival, locomotion, and stress biomarker expression. Oyster larvae exposed to environmentally relevant concentrations (100 ng/L and 1,000 ng/L) of benzoylecgonine, cannabinol, codeine, fentanyl, ketamine, and methamphetamine exhibited reduced survival, impaired swimming behavior, and increased expression of stress-related genes. Mixture exposures further amplified both molecular and physiological effects. In D. magna, neonates exposed to nine DAs (1 µg/L to 20 mg/L, 48 h) showed dose-dependent behavioral toxicity, including hyperactivity or hypoactivity responses, along with changes in the expression of stress biomarkers, particularly under mixture conditions. 

An ecological risk assessment framework was developed using two metrics: (a) Risk Quotients (RQs), derived from LC50 (lethal concentration at 50%) values to estimate relative risk for individual DAs, and (b) an equivalent concentration metric, using methadone as a reference compound, to measure combined toxicity. Application of this framework to regional monitoring data indicated that effluent samples exhibited the highest risk levels, while downstream sites showed comparable risks, suggesting persistence of toxic effects beyond discharge points. Overall, this study provides a comprehensive evaluation of the occurrence, biological effects, and ecological risks of DAs in aquatic environments.